Straight pipes on C3 ???

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Jan 2, 2013 | 09:48 PM

#21

scottyp99

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From: Oxford MA-----You just lost the game!!!!

Quote:

Originally Posted by Doug1

I think you mean to be asking about the rings on the pistons. after some reading online I think that it turns out that is a myth. that it overheats the rings. just what I've read

What is up with the whole "You need some back pressure..." thing? It's just plain silly.

Scott

Jan 2, 2013 | 09:55 PM

#22

Doug1

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Joined: Sep 2012

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From: Palm Harbor, Florida

Quote:

Originally Posted by scottyp99

What is up with the whole "You need some back pressure..." thing? It's just plain silly.

Scott

yeah, I don't know either, but having said that, I am leaning toward believing the scavenging thing

Jan 2, 2013 | 10:50 PM

#23

wcsinx

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Joined: Mar 2002

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Quote:

Originally Posted by scottyp99

What is up with the whole "You need some back pressure..." thing? It's just plain silly.

Scott

No it isn't. But the answer isn't as simple as yes/no. It depends on what you plan on doing with the car/engine.

Jan 3, 2013 | 10:19 AM

#24

Danish Shark

Burning Brakes

Joined: Aug 2008

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From: Deep South Denmark

Back pressure is for two-stroke engines...

Jan 6, 2013 | 10:30 PM

#25

Chambered

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From: Milford Michigan

Quote:

Originally Posted by briankeery

Can running a car with no back pressure be OK for the valve train?

Chrysler was doing a lot of experimenting on Vipers trying to get the V-10 exhaust to sound good - not an easy task. On one test mule, they ran straight pipes & dynoed the car. Engine ran hot & made less HP. They let it cool down & then installed a pair of mufflers. Temp came back into range & HP went back up. After hearing this, I would never run straight pipes. The exhaust system benefits from some sort of expansion chamber, a glasspack, oval muffler, etc. Plus, straight pipes do not tune the sound at all, nor do most mufflers for that matter. Also, as far as backpressure, you'll get that from running the correct diameter pipes in addition to the muffler.

Jan 7, 2013 | 11:30 AM

#26

wcsinx

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Quote:

Originally Posted by Chambered

I have a hard time believing peak HP went down with straight pipes. Though across the curve it very well could have.

Jan 7, 2013 | 02:37 PM

#27

7t9l82

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From: melbourne florida

2023 C3 of the Year Finalist - Modified

Quote:

Originally Posted by Chambered

that is only a sign the air fuel mixture is wrong and probably the timing too. i say B.S

Jan 7, 2013 | 04:06 PM

#28

johnt365

Drifting

Joined: Dec 2004

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From: Austin Texas

I just had 2.5 in pipe run from my headers back. I put some pics on this post. http://forums.corvetteforum.com/c3-t...ffler-pic.html

I chose a straight through muffler. These will flow plenty for my 350.
They have a nice deep tone.

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Jan 7, 2013 | 04:17 PM

#29

scottyp99

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From: Oxford MA-----You just lost the game!!!!

Quote:

Originally Posted by 7t9l82

that is only a sign the air fuel mixture is wrong and probably the timing too. i say B.S

I agree. I think that may have something to do with how the whole myth started. People would make exhaust mods that decreased backpressure, and see performance decline, and say "Hmm, the engine must need a certain amount of backpressure.". But, in reality, what they did was screw up the tune of the engine. If you decrease backpressure, and then tune for it, you'll see more power. wcsinx may be right, in that in certain situations, and for certain uses, a certain amount of backpressure may be desirable, but, in general, the less backpressure, the better. It is difficult to make blanket statements that have absolutely no exceptions, especially when it comes to how an engine makes power, there are so many variables to take into consideration.

Scott

Jan 7, 2013 | 07:06 PM

#30

Wrecked82

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Joined: May 1999

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From: Texas

Quote:

Originally Posted by johnt365

Look like my Borla's on my 82. Sound is nice and throaty for a low HP engine. Sounds much more powerful than it is. Even received a trophy one time for best sounding car.

Jan 7, 2013 | 08:57 PM

#31

gcusmano74

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If you are going to try open pipes, you will most likely need to recalibrate the carb. When I changed my (stock type) mufflers to Magnaflows, I had to richen things up a bit.

Jan 7, 2013 | 09:06 PM

#32

johnt365

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Joined: Dec 2004

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From: Austin Texas

I am so glad I read this forum. On my way back from the muffler shop after the new pipes I was rolling at around 60mph and then did a gradual WOT. Just when things were really kicking in, I had a back fire and let off. I have an A/F ratio gauge but did not notice the reading. A lean condition would explain it though.

Jan 7, 2013 | 09:21 PM

#33

wcsinx

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Quote:

Originally Posted by scottyp99

in general, the less backpressure, the better.

Not to pick nits, but generally speaking you do want some degree of backpressure. The exception case is a engine that spends most of its life at WOT (1/4 mile cars, dyno queens). If your only concern is peak HP, then yes you want absolutely no backpressure. You could take the exhaust plumbing off and blow it straight out the ports for that matter, but that engine will not be streetable IMHO. That is to say, it will generate less HP and torque throughout the majority of its RPM range, it'll run rougher, throttle response will suffer, and it'll be noisy as chit. (but it will make more peak HP)

Jan 7, 2013 | 10:10 PM

#34

aussiejohn

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From: The only Corvettes in Highett Victoria

Freakkkkky!!!!

Quote:

Originally Posted by wcsinx

Yeah, he actually closed the Wickham Rd. shop because he was getting more business than he could handle with only 4 bays. He's off Old Nasa Blvd now.

I'm also in Melbourne, not far from Wickham Road in Highett, but there's this ocean thing between us, the Pacific or sumfin.

Regards from Down Under.

aussiejohn

Jan 7, 2013 | 10:12 PM

#35

wcsinx

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Quote:

Originally Posted by aussiejohn

I'm also in Melbourne, not far from Wickham Road in Highett, but there's this ocean thing between us, the Pacific or sumfin.

Regards from Down Under.

aussiejohn

I thought you were joking, but I had to check google maps anyway. There actually is a Wickham Rd. in Melbourne AUSTRALIA as well.

Jan 8, 2013 | 05:09 AM

#36

7t9l82

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From: melbourne florida

2023 C3 of the Year Finalist - Modified

shame they don't connect.

Jan 8, 2013 | 11:35 AM

#37

Snoopysvet

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Joined: Oct 2006

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From: El Cajon California

Quote:

Originally Posted by scottyp99

What is up with the whole "You need some back pressure..." thing? It's just plain silly.

Scott

Is the scavaging more important than relieving back pressure?

So leaving the headers off and running nothing as opposed to running open headers?

curious

Jan 8, 2013 | 12:07 PM

#38

wcsinx

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Quote:

Originally Posted by Snoopysvet

Is the scavaging more important than relieving back pressure?

During a partial throttle cruise condition typically yes

At WOT ... no

Jan 8, 2013 | 12:23 PM

#39

johnt365

Drifting

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From: Austin Texas

So if scavenging comes into play more at part throttle, and less back pressure at WOT, is it possible that better scavenging improves economy and mileage and less back pressure improves performance?

I realize the scavenging is increasing performance but at part throttle it may be more of an economy factor.

How about this, when I punch it, is it safe to say I want less back pressure?

Jan 8, 2013 | 12:47 PM

#40

wcsinx

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Quote:

Originally Posted by johnt365

Without any scavenging effect, you will see lower power and torque numbers across the majority of the curves. (or at least the part of the curve that's used the majority of the time in day-to-day driving)

And in this context, what is it to improve economy other than to generate more power with the same amount of fuel?

Quote:

How about this, when I punch it, is it safe to say I want less back pressure?

Even then it's not that simple. If you punch it at low RPM, then the exhaust velocity might still be low enough that you would benefit from some backpressure and/or scavenging. Once you get up to 4k-5k? RPM probably not. Did you know the C6Z has variable valving (actuated by engine vacuum) in its exhaust setup?

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